Chiang Mai Journal of Science

Biogas was obtained from the hydrolysate and solid fraction of microwave acid pretreated Napier grass by anaerobic mixed cultures. Factors influencing methane production including initial pH, inoculum concentration, and carbon to nitrogen ratio (C/N ratio) were investigated. For the hydrolysate of Napier grass, maximum methane production (MP) and methane production rate (MPR) of 621.31 mL-CH₄/L and 0.72 mL‑CH₄/L h were obtained at initial pH of 8 and inoculum concentration of 15 g-VSS/L. Using the solid fraction of pretreated Napier grass co-digested with swine manure, maximum MP and MPR of 630.05 mL-CH₄/L and 0.74 mL‑CH₄/L h were obtained at C/N ratio of 21.03. Main methanogenic bacteria found in the hydrolysate and solid fraction fermentation of pretreated Napier grass co-digested with swine manure were Methanosarcina sp. Methanoregula sp. Methanospirillum sp. Methanocullues sp. and Methanothrix sp. Overall energy production from Napier grass hydrolysate and the solid fraction of pretreated Napier grass co-digested with swine manure was 7.99 kJ/g-VS_added.